I don't know about that. I have been told the opposite from older industry professionals. When I worked with the talent agency, their goal was to be the first entertainment company for venues and planners in the area to refer. The owner attended every networking event he could. They built their business on referrals from venues and planners in the region. Sure, they would get repeat customers, and general word of mouth referrals from previous clients, and take leads on wedding wire too, but the backbone of their business came from venue and planners referring them to new clients corporate and weddings.
I get a good chunk of my bookings from past customers referring me. However, those referrals aren't always the best. Often, they come in, and I am already booked on that date. Or they weren't expecting to spend as much at my price point. I had one earlier this year where I was referred from a wedding client from 2 years ago. The couple only had a budget of $1,100 and wasn't willing to go over it, and their wedding venue was a long drive. At least they contacted me, but they didn't want to spend $1650. That also told me they didn't look at my website first. Otherwise, they would have seen the pricing.
Also, a lot of my work are from families coming from other areas of the country or the couple coming from other areas. The DC area is very transient. If the couple is only getting married here, but live in Colorado for example, and their friends are out that way...I'm unlikely to get a referral from that couple. Many couples get married here because their parents are in the area, or just one of their parents and some relatives live here. The wedding I am doing this Saturday night, like 80% of the guests are staying at a local hotel because they flew in from other areas. The Groom's family is from Wisconsin. He chose to do a Polka song for the mother/son dance because of their family's heritage even though he knows very little about polka music or dancing to it himself. The bride's family is from all over, but they have some Italian in them. When I work at one of my preferred venues, the odds of the guests and the bride/groom being local Marylanders are much higher.